7 March 2014 Metal-cavity submonolayer quantum-dot surface-emitting microlasers
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Abstract
Metal-cavity submonolayer (SML) quantum-dot (QD) microlasers are demonstrated at room temperature under continuous-wave electrical injection for 2-μm-radius devices and pulsed operation for 0.5-μm-radius devices. Compared to our previous quantum well devices, the superior optical properties of SML QDs provide the possibility for further size reduction. Size-dependent lasing characteristics are extracted from measurements to investigate the device physics for future size reduction. An optical cavity model using the transfer matrix and the effective index method including metal dispersion is developed and used for both the design and the experimental results analysis. The laser uses an active region consisting of three groups of SML QDs, and each group consists of 10 stacks of 0.5-monolayer InAs QD layers. The cylindrical microcavity is formed by hybrid metal-distributed Bragg reflectors (DBRs) mirrors with an optimized SiNx passivation layer on the sidewall to reduce the metal loss and to avoid the leakage current. The transverse optical modes are solved using the Maxwell equations, and the resonance condition is determined by roundtrip phase matching. Vertically-correlated QDs are modeled as quantum disks, and the wave functions and eigenenergies in both conduction and valance bands are solved from Schrodinger equation. Carrier-dependent material gain is calculated using Fermi’s golden rule and included in the model. The lasing wavelengths, quality factors, and confinement factors for cavity modes are the inputs for the rate-equation model, which predicts the light output power vs. current behavior and has shown excellent agreement with experiments. Size-dependent physical quantities such as leakage current and spontaneous emission coupling factor are extracted and investigated. Further size reduction using only four pairs of DBRs is proposed.
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Pengfei Qiao, Chien-Yao Lu, Dieter Bimberg, Shun Lien Chuang, "Metal-cavity submonolayer quantum-dot surface-emitting microlasers", Proc. SPIE 8980, Physics and Simulation of Optoelectronic Devices XXII, 89800E (7 March 2014); doi: 10.1117/12.2042210; https://doi.org/10.1117/12.2042210
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